Image assistance for indoor positioning

ABSTRACT

A method for tracking collector devices in an indoor area associated with imaging devices and RF signal sources covering the area includes generating aspects of a plurality of coarse position tracks of the collector devices based on RF signal measurements obtained by the collector devices from the RF signal sources. Imaging devices capture image frames of the collector devices in the indoor area which are then processed in order to determine aspects of a plurality of fine position tracks of the collector devices. The server and the collector device communicate with each other and match aspects of at least one of the fine position tracks to the aspects of the coarse position track of the communicating collector device in order to determine the precise location of the collector device in the indoor area.

FIELD OF INVENTION

The present invention is directed toward indoor positioning of mobiledevices and in particular to systems and methods for tracking mobiledevices using a combination of image processing and coarse location dataproviding trajectory information of the mobile devices.

BACKGROUND

Outdoor positioning of a collector device (e.g. a mobile device) can beachieved using Global Navigation Satellite System (GNSS). Inconventional GNSS, the mobile device may collect information from thesatellites along a line-of-sight. The collected information may then beused to compute the location (longitude, latitude, altitude) of themobile device to within a few meters. A mobile device may also determineits position by triangulating signals from cell-phone transmitters.

SUMMARY OF THE INVENTION

An example embodiment of the present invention includes a method fortracking collector devices in an indoor area associated with and imagingdevices. The method includes generating aspects of a plurality of coarseposition tracks of the collector devices based on sensor measurementsmade by the collector devices. Imaging devices capture image frames ofthe collector devices in the indoor area which are then processed inorder to determine aspects of a plurality of fine position tracks of thecollector devices. The server and the collector device communicate witheach other and match aspects of at least one of the fine position tracksto the aspects of the coarse position track of the communicatingcollector device in order to determine the precise location of thecollector device in the indoor area.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawings, with likeelements having the same reference numerals. When a plurality of similarelements are present, a single reference numeral may be assigned to theplurality of similar elements with a small letter designation referringto specific elements. When referring to the elements collectively or toa non-specific one or more of the elements, the small letter designationmay be dropped. The letter “n” may represent a non-specific number ofelements. Also, lines without arrows connecting components may representa bi-directional exchange between these components. According to commonpractice, the various features of the drawings are not drawn to thescale. Also, the dimensions of the various features are arbitrarilyexpanded or reduced for clarity. Included in the drawings are thefollowing figures:

FIG. 1A is a block diagram depicting one embodiment of a system fortracking a collector device.

FIG. 1B is a diagram depicting video stream showing multipletrajectories of collector devices captured by imaging device(s) as shownin FIG. 1A.

FIG. 1C is a diagram showing multiple fine position tracks correspondingto the trajectories of the collector devices as shown in FIG. 1B.

FIG. 1D is a diagram illustrating the matching of a coarse positiontrack to one of the fine position tracks as shown in FIG. 1C.

FIG. 2A is a block diagram showing one embodiment of a collector device.

FIG. 2B is a block diagram depicting one embodiment of a server.

FIG. 3 is a flow-chart diagram depicting the high level processes fordetermining a location of a collector device.

FIG. 4 is a flow-chart diagram of an embodiment depicting a method of acollector device receiving position information for determining aprecise location of the collector device, as shown in FIG. 3.

FIG. 5 is a flow-chart diagram of an embodiment describing a method of aserver receiving and transmitting position information, as illustratedin FIG. 3.

FIG. 6 is a flow-chart diagram of an embodiment depicting a method of animaging device capturing image frames, as shown in FIG. 3.

DETAILED DESCRIPTION

Outdoor positioning of a collector device can be achieved by employingGNSS or by triangulating signals from cell-phone transmitters. Forindoor positioning, however, GNSS, and or cell triangulation may not besuitable because it may be difficult to receive the signals. Inaddition, cell triangulation may pose further difficulties because ofantenna characteristics, reflections and obstructions in the indoorenvironment. Embodiments of the invention overcome the limitations ofindoor positioning by tracking a collector device in an environmentcovered by a set of imaging devices (video or still-frame) andmonitoring RF signal characteristics of RF signal sources. Particularly,a collector device can obtain aspects of a coarse position track basedon measurement sets including signal characteristics of RF signalsources in the indoor area and sensor data indicating the displacementand direction of the collector device along a path. In addition tosignal measurements, aspects of the coarse position track may include,for example, left turn, right turn, u-turn, acceleration, deceleration,etc, performed by the collector device. For example, the some of theseaspects of coarse position tracks may be derived from the signalsprovided by pedestrian dead reckoning (PDR) devices.

The collector device may also obtain aspects of its fine position trackbased on images by the imaging devices covering the indoor area.Specifically, imaging devices can capture multiple digital images, eachcomposed of a plurality of pixels that can be statistically mapped topositions. Groups of contiguous pixels in image frames that movetogether are considered to be one object. Standard techniques, such asusing comparison of an image frame including an object with anotherimage frame with an empty scene, pixel differences from frame to frame,object recognition, etc., may be used to determine motion and eventuallythe trajectory information of collector device(s) or person(s) carryingcollector device(s) in the indoor area, for example.

A server may receive the fine position tracks from the imaging devicesand aggregate the fine position tracks, which may include combiningoverlapping fine position tracks captured by at least two differentimaging devices, into a single fine position track, for example.Alternatively, the fine position tracks may be aggregated by the imagingdevices.

The collector device can further communicate with the server, based onthe coarse position data, receive the fine position track informationand match aspects of the coarse position track to the aspects of one ofthe fine position tracks in order to locate the position of thecollector device accurately. The aspects of the fine position tracks maybe within the uncertainty of the coarse position tracks, for example.

In one example, the indoor environment may be a retail store, and aperson in possession of a collector device may anonymously locate his orher position accurately, based on the coarse and the fine positiontracks, as described above. The person can further navigate to a desiredlocation by making accurate turns based on the aspects of the providedposition tracks and indoor maps.

Position information may be collected for persons or objects (e.g.mobile equipment). The object or person typically includes a collectordevice. In the materials that follow, the term “object” includes aperson.

FIG. 1A illustrates a system 100 for determining the location of acollector device 102 in accordance with an embodiment of the presentinvention. The illustrated system includes a plurality of collectordevices 102 a-n (only four devices 102 a-d are shown in FIG. 1A), aplurality of imaging devices 108 a-n (only four imaging devices 108 a-dare shown in FIG. 1A) coupled to a server 104, and a plurality of RFsignal sources 106 a-n (only four RF signal sources 106 a-d are shown inFIG. 1A). The example imaging devices 108 a-d are coupled to the server104 via the network 110 (wired or wireless).

The RF signal sources may be, for example, any terrestrial RFtransmitter or transmitter/receiver of wireless or RF signals, forexample, IEEE 802.11 access points. The collector devices may be, forexample, mobile telephones, or IEEE 802.11 devices that are configuredto receive the RF signals transmitted by the RF signal sources 106 a-d.The RF signals may include information, for example, access pointidentifier (e.g. media access control identifier (MAC ID), receivedsignal strength indication (RSSI), time or phase offsets of receivedsignals and/or round-trip delay time (RTT), which may be processed bythe collector device 102 in order to determine aspects of a coarseposition track.

Each collector device 102 may also or alternatively include sensors thatdetermine a coarse position track by comparing the respective RSS valuesfor the signal sources 106 to a set of access point “fingerprint” dataindicating the relative strengths of the sources at different positions.The coarse positions may also be determined using trilateration of thesources 106 or using the cell identity of nearby cellular transmitters.

The imaging devices 108 may be, for example, networked cameras, that areconfigured to capture still-frames or video. In one embodiment, theimaging devices 108 may be monochrome or color cameras. Alternatively,the imaging devices 108 may be infra-red cameras or a combination ofcamera types.

Image processing may also be performed by the imaging devices in orderto determine the aspects of the fine position tracks of the collectordevices. This may reduce the burden of data on the network 110.Alternatively, image processing may be performed by the server 104, forexample.

The server 104 may be configured to receive the fine position trackinformation from the imaging devices 108 via the network 110.Alternatively, if the server 104 is configured to perform imageprocessing in order to determine the fine position track information, itmay then directly receive image frames from the imaging devices. Theserver 104 may send the fine position track information to a collectordevice 102, for example, upon responding to the requesting collectordevice 102.

FIG. 1B illustrates respective positions of four objects derived from avideo stream including multiple image frames captured by an imagingdevice 108 a. Alternatively, the video stream of FIG. 1B may begenerated by multiple imaging devices, for example, imaging devices 108a-d. The video stream 120 includes fine position trajectories of thecollector devices. As another alternative, video stream 120 may includefine position trajectories of objects. In one example, as shown in FIG.1B, trajectory 126 depicts the motion of the collector device 102 b, ora person (not shown) in possession of the collector device 102 b,captured in different image frames. For example, in one image frame, thecollector device 102 b may be at a point b-1 at a specific time. Inanother instance, the collector device 102 b may move to a next pointb-2 captured in a different image frame. Yet in another time, the imageof the collector device at a point b-3 may be captured in an other imageframe. Thus, different image frames capturing the positions, b-1, b-2and b-3 of the collector device 102 b at different times, may beconsecutively processed in order to generate the trajectory 126.Trajectories may be generated, for example, when the image frames areprocessed. Image processing may include comparison of an image frameincluding a collector device to an image frame with an empty scene,pixel differences between consecutive frames, object recognition, etc.,in order to determine the motion of a collector device or an object. Forexample, 122, 124, 126, 128 are the trajectories of the collectordevices 102 a, 102 b, 102 c and 102 d, respectively. A trajectory of anobject may be a segment of the corresponding track, for example.

In an another embodiment, an object may be in a still position. As such,maintenance of trajectory information may be terminated after apredetermined amount of time (e.g. 1 to 5 minutes). Tracking may resumewhen the object moves again.

FIG. 1C illustrates the fine position tracks of the collector devicescorresponding to the trajectories of FIG. 1B. For example, a fineposition track set 130 including fine position tracks 132, 134, 136, and138 correspond to the fine position trajectories, 122, 124, 126 and 128,respectively. The fine position tracks are generated based on thecalibration of the imaging devices such that each pixel in an imagestream is assigned to known coordinates.

The coordinates may be based upon a standard coordinate system such asWGS84, for example, providing longitude, latitude and altitudeinformation.

Biometric or other information about the objects, for example, height,color or size may further assist in the mapping of the image position toan actual position (with coordinates). The tracks can be aggregatedlocally at a control point and sent to server 104. For example, theindoor area may have several floors with each floor having a controlpoint. Thus, each of the control points of the respective floorscollects the aspects of the fine position tracks from the imagingdevices covering the respective floor. In this example, the controlpoints of each floor may then aggregate the aspects of the fine positiontracks and send them to the server 104.

Alternatively, the tracks may be sent to the server 104 directly via thenetwork 110, for example. Communications to and from the server 104 maytake place over secure links.

Calibration of the imaging devices may be implemented in order to assigna position to each pixel in an image. Calibration of the imaging devicesmay be performed during a setup stage and is described in detail below.Calibration points may be chosen in the indoor area for calibrating allof the cameras, for example. The calibration points, captured in animage by the specific camera, for example, may be assigned to knowngeometrical coordinates (latitude, longitude, altitude). Thereafter, anyspecific point in the image may be interpolated and mapped back to acorresponding specific location in the indoor area covered by the image.This results in the cameras being calibrated to the same coordinatesystem.

In an another embodiment, each imaging device 108 covering the indoorarea may be calibrated individually with its own set of coordinates. Forexample, each camera may track an object (e.g., a person walking) in theindoor area and generate aspects of a fine position track based on itscalibrated coordinate system. The fine position tracks of the objectgenerated in different coordinate systems may then be sent to the server104. The server may identify corresponding objects in the images, mayprocess the aspects of the tracks and warp the different coordinatesystems into a common coordinate system, using for example, affine orparametric transformations. In an another example, the server may relayback a set of reference images captured in the common coordinates to thedifferent imaging devices. The imaging devices may then warp theircoordinate systems to the common coordinate system and perform furthertracking based on the common coordinate system, for example.

Alternatively, calibration of the imaging devices may not be necessary,if stereo images are captured by the imaging devices having knownlocations and focal lengths.

As described above, at the point of aggregation, duplicate tracks fromrespectively different images may be combined into a single track. Forexample, trajectories (not shown) similar to the trajectory 122 as shownin FIG. 1B of the collector device 102 a, may be generated by theimaging devices 108 a and 108 b based on different viewing perspectives.However, the tracks (not shown) corresponding to the trajectory 122,generated by the imaging devices 108 a and 108 b are similar to eachother. As such, the tracks may be combined into a single track 132,depicting the path taken by the collector device 102 a, as shown in FIG.1C. The combining process may further include the server 104 averagingfine position tracks in a common coordinate system received from theimaging devices 108 a and 108 b in order to generate a single track 132,for example.

The collector device 102 may be time calibrated with the imaging devices108 and the server 104, providing a time accuracy between 0.5 and 2seconds, for example. The time calibration may be based on NTP, forexample, and may be periodically updated. Further, the fine positiontracks may be received for a predetermined amount of time. For example,the collector device 102 may send a request to the server 104 for theaspects of the fine position tracks that may had been generated withinthe last 5 seconds-10 minutes, from the time of the request.

FIG. 1D illustrates correction of a coarse position track 136′ to a fineposition track 136. At first, aspects of a coarse position track 136′may be calculated by a collector device based on measurement setsincluding signal characteristics of RF signal sources and sensor dataindicating the displacement and direction of the collector device. TheRF signal measurements may include signal strengths of the access points106 a, 106 d, for example. The RF signal measurements may also oralternatively include the roundtrip delay time. Each collector devicemay generate, sensor data, to indicate, for example, a displacement ofthe collector device 102 a along a path and acceleration or decelerationincluding turns. The example collector device may calculatedisplacement, acceleration, and environmental information based on itspresent and/or previous location along the path. This information may begenerated by circuitry internal to the collector device, including,without limitation, a Hall-effect or micro electro-mechanical systems(MEMS) magnetometer, a MEMS accelerometer, an optical or MEMS gyroscope,a pedometer, or a MEMS barometer. Thus, the collector device maygenerate successive displacement vectors derived from sensor data, forexample. Each displacement vector may specify a displacement along thex, y, z axes. For example, the collector device 102 a, or an object inpossession of the collector device 102 a, may calculate the track 136′based on PDR.

As shown in FIG. 1D, the collector device 102 a travels along a path136′ and reaches point A′ and collects a time stamp and RSSI and RTTdata based on communication with the RF signal sources 106 a, 106 d, forexample. Collector device 102 a may collect sensor data from a previouspoint on the route 136′ (not shown) to point A′. Collector device thentravels to point B′ while collecting sensor data. At point B′, thecollector device 102 a further collects RSSI, RTT data and time stampdata from 106 a, 106 d. The collector device 102 a then travels to pointC′ and generates sensor data and RSSI or RTT data between the points B′and C′ in a similar fashion. As such, these measurement sets may becollected and processed by the collector device 102 a in order togenerate the aspects of the coarse position track 136′. Alternatively,the collector devices may send the measurement sets to the server 104.The server 104 may then generate the aspects of coarse position tracks,for example.

The coarse position track 136′ may be an estimate because, for example,the collector device 102 a may not have a clear signal path to one orboth of the RF signal sources, as such, the signal characteristics atpoints A′, B′, C′, D′ may be attenuated. In addition, RTT or arrivaltime may be erroneous due to multipath. Furthermore, the sensor data maynot be accurate, as the sensor modules may not be calibrated properly,or due to the presence of materials, that can disrupt the functionalityof the sensor modules (e.g. ferromagnetic materials may disrupt anelectronic compass). Thus, in order to accurately determine aspects of atrack, the collector device may utilize further assistance, for example,image assistance in the form of fine position track information, asdescribed above.

The collector device 102 a, or an object in possession of the collectordevice 102 a, after determining the coarse position track 136′, may thenreceive the fine position track set 130 and compare the aspects (e.g.time-stamped turns) of the fine position tracks (included in the trackset 130) with the coarse position track 136′. Once an unambiguous trackhas been identified, for example, the fine position track 136, a coarsepoint D′ in the coarse position track 136′ may snap to a fine position Dof the fine position track 136, once a correction is applied, as shownby the arrow 135. This may reduce the uncertainty range during the nextimage assistance request to the server, for example.

FIG. 2A depicts a collector device 102 in accordance with aspects of thepresent invention. The example collector device includes at least oneantenna 204, receiver or transmitter/receiver 206, processor 208, memory210 and sensor module(s) 202.

Memory 210 may store instructions for the processor 210 and data used bythe collector device 102.

Processor 208 may be used by the collector device 102 to process datacollected or monitored in order to determine displacements of thecollector device, for example. In addition, the processor 208 maycontrol other functions of the collector device 102. For example, if thecollector device is a mobile telephone, the processor 208 may processaudio information or data transmitted through the communicationchannels.

In general, the collector device 102 includes receiver ortransmitter/receiver 206 to monitor the signal characteristics of the RFsignal sources 106 via the antenna 204 and, in one embodiment of theinvention, transmits aspect of the coarse position tracks to the server104. Alternatively, the transmitter/receiver 206 may transmit the signalcharacteristics of the RF signal sources to the sever 104 via theantenna 204. The collector device 102 may transmit or receiveinformation contemporaneously, at predetermined times or as requested bythe server 108. The transmit/receiver 206, for example, may also receivethe fine position tracks from the sever 104. In yet another embodiment,the transmitter/receiver 206 may not include a transmitter, for example,the receiver 206 (not shown) may receive the fine position tracks fromthe sever 104 and match its position to the fine position tracks usinginternally maintained data.

Sensor module(s) 202 may include, for example, an accelerometer, agyroscope, a compass or magnetometer, a barometer, pedometer, a cameraand/or other components for determining movement (e.g., direction anddistance) of the collector device 102. The RF receiver of thetransmitter/receiver 206 may also be used as a sensor to detect the RSSIof the RF signal sources.

FIG. 2B is a schematic illustration depicting one example embodiment ofa server 104. In this embodiment, the server 104 communicates with thecollector device 102 using its transmitter/receiver 218 via the antenna216.

The transmitter/receiver 218 may be used to receive other messages aswell. For example, the transmitter/receiver 218 may be configured toreceive messages from the collector device 102, for example, the signalcharacteristics of the RF signal sources, in order to determine aspectsof coarse position tracks of the collector devices. Alternatively, thetransmitter/receiver 218 may be configured to receive coarse positiontrack information of the collector devices 102. The server 104 may alsobe configured to communicate with the imaging devices and receive imagesor analyzed position information from the imaging devices. For example,the server 104 may receive raw image frames from the imaging devices108. Alternatively, it may receive the fine tracks or the aspects offine position tracks directly from the imaging devices 108, over thenetwork 110.

The processor 220 included in the server 104 may process the capturedimage frames received from the imaging devices 108 in order to determinethe aspects of the fine position tracks corresponding to the objects inthe captured images, in one exemplary embodiment. The processor 220 mayalso be configured to process data received from the collector device102. Transmitter/receiver 218 may transmit fine position trackinformation in response to requests from the collector device 102. Theprocessor 220 may further process track information in order to map theaspects of the fine position tracks to the aspects of the coarseposition tracks, for example. Memory 222 may store the raw imagesreceived from the imaging devices, in one example. It may also store theRF signal measurement, displacement data and time stamps received fromthe collector devices in order to calculate the coarse position tracks.

FIG. 3 is a flow diagram outlining the high level steps used fortracking a collector device 102 in an indoor environment as shown inFIG. 1A, for example. At step 302, aspects of a coarse position track ofa collector device are generated. For example, the aspects of the tracksmay be based on the measurement sets including RF signal characteristicsof the RF signal sources 106, and/or displacement and direction dataobtained from the PDR sensors. Further, aspects of the coarse positiontracks may be generated by the collector device 102, or alternatively,by the server 104. At step 304, multiple image frames including at leasta collector device, or an object in possession of a collector device tobe tracked in the indoor environment, are captured by the imagingdevices, for example.

At step 306, captured image frames of step 304 are processed to generateaspects of fine position tracks of the collector devices. Processing ofthe images can be performed by the imaging devices and the tracks oraspects of the tracks sent to the server 104, or alternatively, imagesmay be sent to the sever 104, where the images are processed in order togenerate aspects of the fine position tracks of the collector devices.

At step 308, aspects of one of the fine position tracks are matched withthe aspects of one of the coarse position tracks generated at step 302,for example. The collector device may match the aspects of the fineposition tracks with those of the coarse position tracks. Alternatively,the server 104 may be configured to perform the matching operation. Insuch case, the server 104 may receive aspects of the coarse positionsdirectly from the collector device, for example.

FIG. 4 is a flow diagram depicting a more detailed view of the methodused by a collector device 102 in order to accurately determine itsposition in an indoor environment. At step 402, the collector device 102may be configured to monitor the RF signal sources 106 and/or the PDRsensors 202 and collect RF signal and sensor measurements including, forexample, RTT, RSSI, motion or sensor information and time stampinformation. At step 404, the collector device may be further configuredto process the data collected at step 402, in order to determine aspectsof a coarse position track. For example, as described above, and asshown in FIG. 1D, track 136′ may be generated based on PDR. The coarseposition track 136′ may have an accuracy of 5-15 m range, for example.

Alternatively, server 104 may be configured to generate the aspects ofthe coarse position, for example, as mentioned above in the discussionfor step 302.

The collector device 102 may also be configured to receive aspects ofthe fine position tracks from the server 104, for example, as shown atstep 406.

The collector device may also be configured to extract aspects of acoarse position track, for example, by image processing. For example,the collector device may compare time-stamped inflection points with theturns made in the coarse position track. Based on the comparison, it maythen extract and record those features.

At step 408, the collector device 102 may further check whether theaspects of the fine position tracks, received at step 406, lie within anuncertainty range of the aspects of the coarse position tracksdetermined at step 404. For example, the collector device 102 mayreceive the track set 130 containing the fine position tracks, as shownin FIG. 1C, from the server 104. The collector device 102 may thendetermine that the aspects of the fine position track 136 lie within theuncertainty of the aspects of track 136′, as shown in FIG. 1D. Whereas,fine position track 132 is not within the uncertainty range of thecoarse position track 136′, for example. Thus, at step 410, thecollector device 102 may then match the aspects of the coarse positiontrack 136′ to the aspects of the fine position track 136. The matchingprocess may include a step of applying a correction algorithm, forexample, in order to snap the aspects of the coarse position track 136′to the aspects of the fine position track 136, as shown in FIG. 1D. Thismay further reduce the uncertainty range, for example. This may resultin substantially reduced data transfer during the next request for imageassistance from the server 104. Alternatively, if a wrong position trackis locked in during the step 410, the uncertainty range may be increasedfor example, in order to receive a wider range of fine position tracks,thus providing a recovery mechanism.

The received fine position tracks may be used to calibrate PDR sensors.The PDR sensors may then more accurate, making it more reliable and mayfurther make it possible to extend the time before another request forimage assistance is made to the server 104, for example.

FIG. 5 is a flow diagram showing a more detailed view of the method usedby a server 108 providing assistance for accurately determining a fineposition of a collector device in an indoor environment.

At step 502, the server 104 may be configured to receive aspects of aplurality of fine position tracks of collector devices 102 from aplurality of imaging devices 106 covering the indoor environment.Alternatively, server 104 may be configured to process raw image framesreceived from the imaging devices 106 and generate aspects of the fineposition tracks. Furthermore, or alternatively, server 104 may receiveraw image frames with time-stamps, or aspects of the fine positiontracks with corresponding time labels.

As described above, the fine position tracks may be based on differentcoordinate systems. Alternatively, the tracks may be warped into acommon coordinate system by the server 104, for example.

At step 504, server 104 may then aggregate the fine position tracks, forexample. As described earlier, the aggregating process may furtherinclude server 104 combining partial tracks and/or averaging similarfine position tracks from different imaging devices, based on a commoncoordinate system, in order to generate a single track 132.Alternatively, fine position tracks may be aggregated at separatecontrol points and then sent to the server 104.

At step 506, the server 104 communicates with the collector devices 102.For example, the server 104 may receive requests for the aspects of thefine position tracks from the collector devices 102. At step 508, server104 may then respond to the request by sending a track set 120, forexample, as shown in FIG. 1C, to the requesting collector device.

FIG. 6 is a flow diagram illustrating the method implemented by animaging device used to assist in tracking a collector device accuratelyin an indoor environment. At step 602, the imaging devices 108 may beconfigured to capture multiple images of the collector devices 102, asshown in FIG. 1A. For example, multiple image frames of the collectordevice 102 a may be captured by the imaging devices 108 a and 108 bproviding different perspectives. As described above, these images maybe in the same or in different coordinate systems. At step 604, imagingdevices 108 may analyze pixel differences in consecutively capturedimage frames in order to determine trajectories of the moving object.For example, analysis of pixel differences may include further imageprocessing of the captured image frames.

At step 606, based on the analysis of step 604, and as shown in FIG. 1B,motion information of a moving collector device, or trajectories, aredetermined based on the captured images of the collector devices. In oneexample of FIG. 1B, the trajectories may be generated by a singleimaging device 108 a. In yet another example, the trajectories may begenerated by multiple imaging devices 108 capturing images in differentcoordinate systems, or alternatively, capturing images and warping thecaptured images to a common coordinate system.

At step 608, the imaging device may be configured to generate aplurality of fine position tracks based on the trajectories determinedat step 606. As described above, for example, aspects of the fineposition tracks may be derived from an average value of similar trackswith identical coordinate systems. Alternatively, the tracks may bewarped into a common coordinate system and then similar tracks areaveraged to generate a corresponding single track for each of thetrajectories, for example.

At step 610, the imaging devices may be configured to send aspects ofthe fine position tracks to the server 104. Alternatively, the imagingdevices 108 may be configured to send the trajectories to the server104, for example.

The server 104 may then process the trajectories to generate the aspectsof the corresponding fine position tracks and send the aspects of thefine position tracks to a requesting collector device. The requestingcollector device may be configured to match the aspects of the coarseposition tracks to the aspects of at least one of the fine positiontracks in order to determine its fine position.

The invention has been described in terms of example embodiments. It iscontemplated that modifications to these embodiments may be made withinthe scope of the appended claims.

What is claimed is:
 1. A method for determining a fine position of acollector device associated with a server and a plurality of imagingdevices coupled to the server, the method comprising the collectordevice: collecting multiple sets of sensor measurements from at leastone sensor associated with the collector device; determining at leastaspects of a coarse position track based on the multiple sets of sensormeasurements; receiving from the server at least respective one of theaspects of a plurality of fine position tracks imaged by the imagingdevices; and determining the fine position of the collector device bymatching at least the aspects of the coarse position track to theaspects of at least one of the fine position tracks.
 2. The method ofclaim 1, wherein the at least one sensor associated with the collectordevice includes a pedestrian dead reckoning (PDR) sensor and the step ofdetermining at least the aspects of the coarse position track furtherincludes using PDR sensor data to quantify a path, including the aspectsof the coarse position track.
 3. The method of claim 2, wherein the stepof determining at least the aspects of the coarse position track basedon pedestrian dead reckoning (PDR) further includes a step ofcalibrating the PDR using at least the aspects of the fine positiontracks.
 4. The method of claim 1, further including a plurality of RFsignal sources, wherein the collecting step collects sensor measurementdata representing respective signal strengths of at least a portion ofthe plurality of RF signal sources.
 5. The method of claim 1, whereinthe step of receiving at least the aspects of the fine position tracksfurther includes a step of receiving the of the fine position trackslabeled with respective time-stamps.
 6. The method of claim 1, whereinthe step of receiving further includes a step of time calibration of thecollector device with the server and the imaging devices.
 7. The methodof claim 1, wherein the step of receiving includes receiving at leastthe aspects of the fine position tracks over a secure link from theserver.
 8. The method of claim 1, wherein the step of receiving at leastthe aspects of fine position tracks further includes a step of receivingthe aspects of the fine position tracks lying within a region ofuncertainty of the coarse position track to the exclusion of the aspectsof any fine position tracks lying outside of the region of uncertaintyof the coarse position track.
 9. The method of claim 1, wherein theaspects include at least one of a left turn, right turn, u-turn,acceleration and a deceleration.
 10. A method for determining a fineposition of a collector device associated with a server and a pluralityof imaging devices coupled to the server, the method comprising theserver: receiving a plurality of fine position tracks from a pluralityof imaging devices and aggregating corresponding ones of the fineposition tracks; receiving requests from the collector devices foraspects of the fine position tracks and sending the aspects of theaggregated corresponding fine position tracks to the requestingcollector devices.
 11. The method of claim 10, wherein the step ofreceiving further includes a step of receiving aspects of a plurality ofcoarse position tracks of the plurality of collector devicesrespectively.
 12. The method of claim 10, wherein the step ofaggregating the fine position tracks further includes a step ofaggregating overlapping fine position tracks, captured by at least twodifferent imaging devices, into a single fine position track.
 13. Themethod of claim 12, wherein the step of aggregating the overlapping fineposition tracks further includes a step of averaging the overlappingfine position tracks.
 14. The method of claim 12, wherein theoverlapping fine position tracks, captured by at least two differentimaging devices, are in respective coordinate systems and the methodfurther includes a step of transforming the respective fine positiontracks into a common coordinate system.
 15. The method of claim 14,wherein the step of transforming the fine position tracks furtherincludes a step sending reference images in the common coordinate systemto the imaging devices.
 16. A method for determining a fine position ofa collector device associated with a server and a plurality of imagingdevices coupled to the server, the method comprising the imagingdevices: capturing a plurality of image frames of a plurality of movingobjects; wherein each of the image frames comprises a plurality ofpixels; determining motion information of at least one of the movingobjects by analyzing the pixel differences among consecutive imageframes including the moving object; generating a plurality of fineposition tracks based on the motion information of the moving objects;and sending at least aspects of the fine position tracks to the server.17. The method of claim 16, wherein the step of capturing a plurality ofimage frames is performed by a plurality of networked cameras.
 18. Themethod of claim 16, wherein the step of capturing a plurality of imageframes further includes a step of mapping the plurality of pixels to aplurality of coordinate positions.
 19. The method of claim 16, whereinthe step of determining motion information further includes a step ofdetermining motion of contiguous pixels representing the object.
 20. Themethod of claim 16, wherein the step of mapping pixels further includesa step of mapping pixels to biometric information of the moving object.21. The method of claim 16, wherein the step of determining motion ofcontiguous pixels representing the object further includes a step ofdetermining a trajectory of the object.